1. Field of the Invention
The present invention relates to a suspension system for a vehicle. More particularly, the invention relates to an independent rear suspension (IRS) system having a tubular subframe which is capable of mounting directly to a vehicle chassis, thus improving ride comfort and handling safety. At the same time, the suspension system is completely self-contained so that a novice mechanic can easily install it.
2. Description of Related Art
The suspension system of a vehicle connects the axle shafts and the vehicle body to each other. The suspension also controls a position of a tire with respect to the vehicle body for its ideal position during the running of the vehicle, and thus obtains optimal handling safety. It also prevents the axle shaft from directly transmitting an impact or vibration from the road surface to the vehicle body, and in this way prevents damage of the vehicle cargo and improves the ride comfort of the vehicle passengers. Accordingly, the connection of the upper and lower portions of the vehicle""s suspension generally is made to be flexible to absorb the impact from the road surface and durable to overcome a driving force, a braking force, and a centrifugal force applied to the vehicle""s wheels.
Such suspensions described above can be variably classified according to the characteristics of their structures. For example, many vehicles are manufactured with an independent rear suspension (IRS). Two types of IRS systems are common: the trailing arm suspension and the short arm/long arm rear suspension. Most of these IRS systems No include an elongated strut as part of the suspension and a shock or strut tower which forms a portion of the vehicle body. For example, the shock tower or strut tower extends into the trunk of a typical passenger automobile occupying some of the cargo space within the trunk, but otherwise does not interfere with the operation of the trunk. Items can be placed in the trunk of a passenger vehicle on the sides of and around the shock tower with little or no problem. Since the automobile strut typically inclines toward the center of the vehicle, the shock tower not only extends upwardly into the trunk, but laterally into the trunk as well.
It has been found that independent rear suspensions offer many dramatic performance advantages over regular live-axle configurations. The main advantage is that each wheel is able to react to the conditions it is facing without transmitting its motion to the car or to the other wheel. This significantly improves the handling of the vehicle. The wheels hold their alignment better, which can improve braking and acceleration on uneven surfaces. The vehicle has more ground clearance, because the differential is raised and being independently sprung allows the half-shafts and control arms to accept a greater angle. IRS-equipped vehicles corner better because there is less weight shifting as the body tilts into the corner.
Thus, the concept and implementation of IRS is nothing new. In fact, luxury automobiles, racing cars, and custom hot-rods have had them for years, and the designs have become more refined and sophisticated over time.
Until recently, trucks were considered only to be utility vehicles. Trucks were used to move loads or drive through rough terrain. If a truck was driven for recreation, it was off road or on rough terrain, not for cruising, high speed racing, or long distance driving.
However, now that trucks are becoming luxury and recreational vehicles, ride smoothness and handling are more important issues to truck buyers. Further, now that trucks come with luxury interiors and class A exteriors, a ride to match would be desirable.
Several patents relate generally to prior art independent rear suspensions and to vehicle suspensions in general, for example, U.S. Pat. No. 3,362,498 to W. D. Allison, U.S. Pat. No. 4,768,274 to Pinnow, Norris, and Benedict, U.S. Pat. No. 4,817,985 to Enokimoto, et al., U.S. Pat. No. 5,240,279 to Kunert, and U.S. Pat. No. 5,362,091 to Lee.
While several of these patents relate generally to suspension assemblies and independent rear suspensions, as well as suspension strut assemblies, none of the above-mentioned patents teach a tubular subframe for holding a suspension assembly which is mounted directly to a mounting perch for a leaf spring on a standard vehicle chassis. Also, none relate to a suspension conversion system that includes a free-standing, self-contained suspension system including an air cushioning system that can at times accommodate heavier cargo loads within the vehicle while not interfering with normal passenger comfort, handling and operation of the vehicle and a disc brake system.
Therefore, what is needed is a suspension system that is the next evolution, one that is an easy-to-install suspension and one that makes it possible for a truck or sport utility vehicle to have a fully independent suspension. What is also needed is a suspension system that provides that smooth, comfortable ride.
The suspension according to the present invention relates to a rear suspension, more specifically, to an independent rear suspension which is provided with a subframe and an attached self-contained rear suspension assembly.
The present invention also relates to vehicle conversions and more particularly relates to a method for converting a truck or other vehicle body having chassis rails and a rear suspension comprised of original equipment manufacturer leaf springs to a vehicle having a suspension with a subframe and an adjustable rear suspension assembly which is designed to provide a smooth transition from hauling heavy cargo to carrying passengers comfortably.
The present suspension system relates generally to a tubular replacement suspension system for original equipment manufacturer (OEM) rear suspensions and uses at least one of the mounting perches of the OEM leaf springs. The inventive suspension system is free-standing and self-contained, which means it is a complete rear suspension replacement package for passenger automobile and truck applications, including axles, control arms, cushioning systems, hub assemblies, and brake assemblies. The invention""s tubular design mounts to any chassis, load, and wheel configuration. Moreover, while most prior art rear suspension assemblies have a dozen or more bolts attaching it to the chassis, it is relatively simple to remove an old suspension system and install the suspension system of the present invention, generally by attaching just four bolts to the existing chassis and four bolts to the existing differential.
The inventive suspension system consists of a complete suspension system including: a tubular subframe, upper and lower control arms, a differential, half-axles, toe adjustment rods, shocks, springs, and other related parts. In the preferred embodiments, a disc brake system is available to upgrade from drum brakes. Since the system is totally self-contained, it is calibrated appropriately so that all the user needs to do is attach the inventive suspension system to the vehicle to be ready to go. This may be accomplished in as little as an afternoon""s work.
There are two main embodiments of the inventive suspension system. The first is a high performance sport embodiment and the second is a standard embodiment. The standard embodiment is made from mild steel tubular members and generally fits on utility trucks, passenger and sport utility vehicles. In the high performance embodiment, the tubular members may be made from a metal matrix composite alloy made from aluminum and boron and sold under the trade name BORALYN(copyright), or other composite materials, like carbon fiber or similarly related fabric materials. These composite materials give the tubular members better performance and strength, as well as a sportier look.
The inventive system consists of a subframe made up of a multitude of tubular members. The subframe mounts to the existing leaf spring mounting perches on the rails of a standard vehicle chassis. In the preferred embodiments, the subframe may be constructed of oval or rectangular tubular members, however, generally any member of any geometric shape may work. For example, the various embodiments may have square or rectangular tubular members. The two tubular members are linked together by an internal subframe structure which is constructed of cross braces and intermediate tubes made of generally round metal tubes. These cross braces and tubes are preferably welded together.
A differential is attached to the cross braces of the subframe via a pair of differential mounts. Upper and lower control arms connect to mounts or mounting ears attached to the intermediate tubes and cross braces of the subframe.
The actual cushioning elements of the suspension assembly may use various configurations of push rods and/or rocker arms activated coils-over-shocks and/or air springs. Shocks and/or push rods may mount to the lower control arm. The shocks may utilize a coil-over-spring and an air spring on the heavy-duty models. In the case of a push rod, it pivots on a rocker, pushing against the shock to its anchor. The coil-over-spring and/or air spring takes over the stabilizing function of a torsion bar, eliminating the complexity and extra parts the torsion bar may require.
An anti-roll bar may mount from lower control arms to the subframe, and may be either a bar style or an adjustable tube and/or blade configuration (race style). A spindle/knuckle mounts to the control arms via bushings or ball joints. Drive shafts (i.e. half-axle shafts) mount from the differential to the drive flange on a knuckle utilizing universal joints or constant velocity joints.
The system may also include a disc brake system including, a master cylinder, metering block, portioning valve, calipers, rotors and associated hardware for upgrading the rear brakes. Most drum brake systems do not fit with the inventive suspension system, and therefore, these existing systems may need to be replaced. For the high performance model, high performance disc brake assemblies such as the assemblies found on 1997 DODGE(copyright) VIPER(copyright) model cars may be supplied. The 4xc3x974 model has either disc brakes like the ones found on 1997 FORD(copyright) THUNDERBIRD(copyright) model cars or brakes which can be purchased from after-market companies. The brakes mount to the upright or knuckle and the rotors mount to the drive flange opposite the U-joints or constant velocity (cv) joints. Tires and wheels mount to the drive flange via lug studs.
The subframe, cross braces, control arms, anti-roll bar, and linkages (if used) are custom-engineered components. The remaining components including differential, half-shafts, main drive shaft, knuckle/drive hub assembly, rear toe adjustment, and disc brake system are over-the-counter, stock components. The high performance model incorporates a differential, brake system, and the spindles/steering knuckle found on 1997 DODGE(copyright) VIPER(copyright) model cars. However, the 4xc3x974 standard model uses the 9 inch, 8.8 inch or DANA(copyright) 44, 60 or 70 series gear differential found on 1997 FORD(copyright) trucks.
Again, the suspension system of the present invention can be easily attached directly to the existing chassis of the vehicle. None of the prior art suspensions are mounted to a subframe that bolts directly into the chassis using the factory given suspension leaf spring mounting perches.
Moreover, the inventive suspension assembly bolts into the subframe and is a complete unit which is self-contained and free-standing. This system includes properly calibrated and designed shock mounting areas, suspension pick up points and rear end carrier points. None of the prior art systems are self-contained, free-standing and functional on their own as is the inventive suspension system.
In summary, the inventive suspension system is unique because of: 1) its tubular structure, 2) the fact that it is also a complete unit which is self-contained and free-standing system and which does not rely on any surrounding structures to mount itself other than original chassis leaf spring mounting perches, and 3) the fact that all the system""s moving components including adjustable shock absorbers, springs, upper and lower control arms, links, disc brake system and all adjacent parts are a part of this self-contained system and do not rely directly on the original chassis to properly function.
It is the object of the invention to create a tubular vehicle suspension system that is a complete unit that is self-contained inside a subframe that bolts directly to a vehicle""s chassis using the factory-given suspension leaf spring mounting perches.
It is an object of the present invention to improve a vehicle""s conversion from hauling cargo loads to carrying passengers.
It is another object of the present invention to improve general vehicle chassis stiffness and handling.
It is yet another object of the present invention to make the rear of any vehicle fully independent, giving that vehicle the ride and handling qualities of luxury cars.
It is still another object of the present invention to improve vehicle ground clearance and suspension travel.
Still another object of the present invention to increase the ease of installation by having suspension systems specifically designed and calibrated for each brand and model of vehicle.
It is yet another object of the present invention to reduce a vehicle""s unsprung weight and tire wear.